1. Field of the Invention
The present invention relates to a self-boosting electromechanical vehicle brake including disc brakes and other types of brakes intended for use particularly in motor vehicles.
1. Description of the Prior Art
One vehicle brake known from German Patent Disclosure DE 101 51 950 A1 is embodied as a disk brake. This known vehicle brake has an electric motor and a spindle drive as its electromechanical actuating device for pressing a friction brake lining against a brake disk for generating a brake force. The brake disk forms a brake body for the vehicle brake. A step-down gear may be connected between the electric motor and the spindle drive. The spindle drive forms a rotation/translation speed-changing gear. In addition, for pressing the friction brake lining against the brake body, still other rotation/translation speed-changing gears are possible, such as a rotatable cam. It is also conceivable for example to replace the electric motor with an electromagnet.
As its self-boosting device, the known vehicle brake has a wedge mechanism, with a wedge that is located on the back side, facing away from the brake disk, of the friction brake lining. The wedge is braced on an abutment that extends at a wedge angle obliquely to the brake disk in the direction of rotation of the brake disk. Between the abutment and the brake disk, there is a wedge gap that narrows in one direction of rotation of the brake disk. The wedge need not be a wedge in the strictest sense; it may also be a non-wedge-shaped element that, together with the abutment, generates a wedge effect.
For braking, the friction brake lining is pressed by the electromechanical actuating device against the brake disk that forms the brake body. The friction brake lining may be displaced either transversely or obliquely at a wedge angle or some other angle. The rotating brake disk exerts a frictional force, in the direction of the narrowing wedge gap between the abutment and the brake disk, on the friction brake lining that is pressing against it for braking; this frictional force, via a wedge effect of the wedge braced on the abutment, generates a reaction force that has a force component transversely to the brake disk. This force component is a contact pressure which, in addition to the contact pressure exerted by the actuating device, presses the friction brake lining against the brake disk. The contact pressure and the braking force are increased as a result. The self-boosting device converts the frictional force, exerted by the rotating brake disk on the friction brake lining pressed against it, into an additional contact pressure. The self-boosting is operative only for one direction of rotation of the brake disk. A displacement of the friction brake lining should be effected on a curved path whose center is approximately on an imaginary axis of rotation of the brake disk, or on a straight path in the secant direction to the brake disk. For attaining the self-boosting action, the frictional force exerted by the rotating brake disk on the friction brake lining must act upon the friction brake lining in the direction of the narrowing wedge gap between the abutment and the brake disk.
Instead of a wedge mechanism, a ramp mechanism which has a curved course for instance instead of a straight course may be used. For rapidly overcoming an air gap between the brake disk and the friction brake lining at the onset of a braking event, the ramp mechanism initially forms a large angle to the brake disk. At high contact and braking forces, the ramp angle may be selected as an acute angle, to achieve a high self-boosting factor.